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Head and Neck and CNS > Thyroid > Flashcards

Thyroid Flashcards

1
Q

where does the thyroid sit

A

C5-T1
in the anterior portion of the neck

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2
Q

what is its relations

A

ant: pre-tracheal muscles + skin
post: four parathyroid glands, one at each upper pole and one at each lower pole of each lobe. behind the middle portion is the isthmus
sup: larynx

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3
Q

what is it lined with

A

cuboidal epithelium

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4
Q

what does the thyroid follicles produce

A

thyroglobulin

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5
Q

what does the central cavity store and secrete

A

colloid
thick sticky protein which contains thyroglobulin attached to iodine, which helps in the hormone production

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6
Q

what surrounds the thyroid follicles

A

parafollicles which secrete calcitonin

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7
Q

what do thyroid follicles do

A

manufacture, store and secrete hormones

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8
Q

what does thyroglobulin contain

A

tyrosine which binds with iodine to produce T4 and T3 in iodine trapping

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9
Q

T4

A

two tyrosine moles and 4 iodine [major hormone secreted]

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10
Q

T3

A

two tyrosine and three iodine
formed mainly in the conversion at target tissues

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11
Q

what does the thyroid wrap around

A

the thyroid cartilage

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12
Q

what is the blood supply

A

highly vascular
supplied by the R + L superior thyroid arteries which are branches of the external carotid arteries
R+ L inferior thyroid arteries are branches of the subclavian
isthmus -> thyroid ima artery os a branch from the external carotid
venous: via a network at the surface of the gland: thyroid veins which are drawn into the internal jugular vein

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13
Q

is it a rare cancer

A

yes

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14
Q

aetiology

A

areas of nuclear disaster
previous RT
autoimmune conditions
genetic factors

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15
Q

what are the five pathology types

A

papillary
follicular
anaplastic
medullary
malignant lymphoma

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16
Q

what are the differentiated types

A

papillary and follicular

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17
Q

describe papillary

A

common, slow growing, finger like projections of stroma

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18
Q

describe follicular

A

occur in patients with goitre
appears solid, solitary, well circumscribed mass
minimal or widely invasive

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19
Q

what can be tracked with differentiated tumours

A

hormone production, as they produce thyroid hormones

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20
Q

what tumours are undifferentiated

A

anaplastic and medullary

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21
Q

describe anaplastic

A

giant or spindle cell
rapid growth and radioresistant

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22
Q

describe medullary

A

arises from para-follicular cells
slow growing
can contain calcium [if not present it indicates a more aggressive tumour]

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23
Q

describe malignant lymphoma

A

non hodgkins
varies from high to low grade

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24
Q

what is a T1a

A

solitary <1cm

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25
Q

T1b

A

multifocal lesion largest <1cm

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26
Q

T2a

A

solitary <2cm

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27
Q

T2b

A

multifocal largest is <2cm

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28
Q

T3

A

lesions >4cm confined within a capsule

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29
Q

T4

A

extension beyond the capsule

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30
Q

what is the follicular spread

A

via the blood stream to lung and bone
likely to metastasise

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31
Q

what is papillary spread

A

regional lymphatics
via deep chain, supraclavicular and paratracheal chain
immobilisation is important for these tumours

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32
Q

what is the anaplastic spread

A

local invasion = neck growth
met to lung, liver and bone early

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33
Q

what is the medullary spread

A

via lymph node and blood stream
high met potential
deposits at the mediastinum are common

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34
Q

what is the lymphoma spread

A

via local LN
recurrence in the GI tract is common

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35
Q

what happens if the thyroid capsule is breached

A

then the trachea, larynx, recurrent laryngeal nerve and skin can be involved

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36
Q

how do all of them spread

A

along the lobe of origin, before spreading to the other lobe via the isthmus

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37
Q

how do PC present

A

solitary mass in one lobe or multiple lesions throughout the gland
enlarged neck nodes [1/3 = bilateral]

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38
Q

FC presentation

A

relate to met spread [jaundice, dysponea (10%) and pathological fracture]

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39
Q

APC presentation

A

rapid and large
nerve pain or vocal palsy due to involvement of the recurrent laryngeal nerve
stridor or dysponsea = tracheal compression
dysphagia = oesophageal compression

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40
Q

MC presentation

A

diarrhoea = secretion of prostaglandins

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41
Q

what produces the pyramidal lobe

A

cell remnants along the tract, lateral parts from the cells in the pharyngeal floor elongates then detaches

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42
Q

what does calcitonin do to calcium levels

A

decreases them

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43
Q

what investigations take place

A

full medical history
examination
indirect laryngoscopy
radiography
FNA
radioactive iodine uptake

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44
Q

what happens at the full medical history stage

A

previous neck RT
family history of thyroid or endocrine disease
previous disease

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45
Q

what happens at the examination

A

neck palpation [masses or scars from previous surgery]
differentiated masses move whilst swallowing whereas undifferentiated are fixed

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46
Q

what is the indirect laryngoscopy for

A

to check for vocal palsy, involvement of the recurrent laryngeal nerve

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47
Q

what is done at the radiography stage

A

plain x ray = calcium deposits/ tracheal compression
US = size and location of suspicious nodules prior FNA

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48
Q

FNA, is it the most reliable

A

yes, in distinguishing between benign and malignant

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49
Q

how can these be managed

A

the management is unclear
relapse is a potential due to under and over treating the patient

most patients are eythyroid which means they have a normal functioning thyroid gland and hormones

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50
Q

what are para-follicles also classed as

A

C-cells
they have a good blood supply

51
Q

what gland and nerve are closely associated

A

para-thyroid gland and the recurrent laryngeal nerve

52
Q

what tumours arise in the follicular cells

A

anaplastic
follicular
papillary

53
Q

what tumour arises in the parafollicles

A

medullary

54
Q

why is a incomplete excision sometimes done

A

some extra-capsular tissue is left to minimise damage to the recurrent laryngeal nerve which runs behind the the thyroid tissue as well as the pituitary gland remaining in tact

55
Q

what is the physiology behind the functioning of the hormones etc

A

Thyrotropin - Releasing Hormone [TRH]
small tri peptide formed in hypothalamus
flows along the neruones to the hypophyseal portal system which supplies the anterior pituitary gland

TSH is released after TRH stimulation
TSH releases T3+T4 from thyroid
as T3+T4 levels increase, TRH decreases, decreasing the TSH secretions

56
Q

what do T3+T4 regulate

A

weight, metabolism, internal temp, skin and hair

57
Q

indications for adjuvant RT

A

incompletely excised or inoperable, well differentiated with inadequate I-131 uptake
medullary carcinoma

58
Q

indications for primary or adjuvant to surgery

A

anaplastic carcinoma to improve local control
not curative

59
Q

what does advanced disease indicate

A

recurrent or mets

60
Q

how are differentiated tumours managed

A

surgery
EBRT

61
Q

describe surgery for differentiated tumours

A

treatment of choice
total thyroidectomy
partial thyroidectomy = leaving 2-3g to influence T3/T4 production
trachestomy = advanced
thyroid ablation is common after surgery

62
Q

EBRT for differentiated

A

HFS supine
CT localisation
shell
chin extended
IMRT uses dose painting for MC
concave PTV, IMRT, 60Gy in 30

63
Q

side effects to RT

A

mucositis
erythema
dry desquamation/ MDS
weightloss

64
Q

how are anaplastic tumours managed

A

radio-resistant therefore palliative RT
AP POP
30Gy in 10
can prevent asphylation due to aggressive tumour

65
Q

what is the prognosis for PC/FC

A

80-90% in 10 years

66
Q

what is the prognosis for AC

A

poor
6 months survival

67
Q

what is the prognosis for MC

A

worse prognosis however if detected early long term survival is possible

68
Q

when is hormone replacement given

A

always
oral thyroxine for the rest of their life
suppresses TSH production for pituitary gland and prevents hypothyroidism

69
Q

describe the location of the parathyroid

A

descends along with the thyroid
two superior at upper pole
two inf
angle of mandible to aortic arch
if enlarged it extends to the mediastinum extension

70
Q

what do the parathyroids do

A

produce, secrete and store para-thyroid hormone

71
Q

what does PTH do

A

regulates calcium and phoshorous in the blood
increases osteoclastic activity
increasing Ca release
increases tubular reabsorption of Ca
increases intestinal reabsorption of Ca

72
Q

what happens when the parathyroid gland is removed

A

PTH levels fall = decrease in Ca levels = increased excitability of neuromuscular tissue = tetancy [twitching]

73
Q

what is the half life for iodine

A

8 days

74
Q

what characteristic do the tumours have which undergo radioactive ablation

A

act in a similar way to normal thyroid
tumours >4cm
gross extrathyroid extension and mets

75
Q

what are the risks to iodine ablation

A

transport source
administration
transport patient
in patient room and surrounding area
waste management and disposal
patient leaving the hospital
readmission of the patient whilst radioactive
post therapy scanning procedures

76
Q

why might repeat surgery/ablation be needed

A

due to it being difficult to ablate lage amounts of normal thyroid

77
Q

where is I-131 found

A

internalised within the cell, beta radiation occurs within the cell
adjacent cells are in the pathway of 0.9mm so are also irradiated

78
Q

what are the systems of work

A

control access
controlled areas
signage
no visitors
no items left in the room
time distance shielding
training
EPDs on entry, ALARP

79
Q

what is the procedure

A

consent
not for pregnant etc
low iodine diet 2 weeks prior [ensure high uptake of I-131]
salt, cough mixture, seafoods, kelp, medications
avoid iv contrast for 2 months prior
TSH levels must be high, TSH IM injections might be given
dose is decided by the MDT

80
Q

what are the doses given

A

early = 1.1GBq + 3.7 GBq
late = 3.7Gbq - 5.5
absorption occurs in the first two hours

81
Q

what is said regarding pregnancy etc after treatment

A

not to get pregnant/father a child for 6 months
stop breast feeding for 8 weeks
limit contact to children and pregnant women

82
Q

what can happen in the first 24 hrs

A

vomitting

83
Q

what hazard is in the first 48 hours

A

urine hazards [highest risk]

84
Q

what hazard happens for approx a week

A

sweating
patient bodily fluids

85
Q

what are the side effects to radioactive ablation

A

bone marrow depression = anaemia, leukopaenia, thromocytopaenia
nausea
neck swelling
taste changes
sialoadenitis = dry mouth
lung fibrosis + acute pneumonitis
radiation cystitis
gastritis
bleeding

86
Q

management for ablation

A

good hydration and laxative

87
Q

what are the late effects

A

dry mouth
abnormal taste
laryngeal oedema
swelling, restricted neck movement
high risk of miscarriage after a year
transient ovarian failure
male infertility
pulmonary fibrosis with lung mets

88
Q

what happens at the follow up

A

diagnostic I-123 scan, 3-6 months after for functioning uptake
probe with a sodium iodide crystal uptake at 2-4 hours and 24 hours
if no uptake the patient might need a full body radionuclide scan to see if there is any functioning mets

89
Q

what does low uptake on the scan indicate

A

hypothyroidism
thyroiditis
recent contrast
exogeneous iodine
antithyroid medication
foods which compete in iodine trapping
ectopic thyroid tissue

90
Q

what happens if further ablation is required

A
  • a dose of 5.5GBq is normally given but can range from 3.7-7.4
  • risk dose to lung is undetected micro mets
  • 1-3 treatments but 6 is the max given
91
Q

follow up

A

life long follow up
detect recurrence
monitor TSH suppression
detect and manage hypercalciaema

92
Q

what is the prognosis for ablation treatment dependent on

A

well differentiated = 5-20% met development
age, size, grade
extrathyroid spread,
distant met spread
lung -> bone -> liver and brain
children <10 years

93
Q

what does I-131 do

A

it travels to the functioning thyroid tissue, where a high dose is given, a low dose is found everywhere else
when all normal thyroid tissue is destroyed the malignant tissue becomes stimulated by TSH and begins to function to replace the missing thyroid

94
Q

what is the MBq of the tracer

A

185

95
Q

what is thyrotoxicosis

A

clinical hyperthyroidism
- overstimulation of TSH receptors
- excess thyroid hormone in body = T3/T4

96
Q

what % is graves disease of thyrotoxicosis

A

60-85%

97
Q

what is the remainder % of thyrotoxicosis

A

nodular thyroid disease

98
Q

what are the tests which are carried out for thyrotoxicosis

A
  • Free T4
  • Free T3
  • TSH
  • thyroid scan I-123 or Tc-99m
  • thyroid uptake I-131
  • graves disease is increased
  • toxic nodular goitre normal or mildly increased
99
Q

signs and symptoms for thyrotoxicosis

A

increased metabolism
raised T3/T4 in blood
agitation
palpitations
diarrhoea
loss of libido
intolerant to heat
fatigue
weakness
sweating
weightloss
protrusion of the eye
fatal cardiac arrhythmia

100
Q

treatment for thyrotoxicosis

A

surgery
antithyroid drugs
beta blockers
RAI 131 - treatment of choice, highly effective, easy and safe

101
Q

describe radioiodine therapy

A

can be ablative or non ablative
stop meds
dose = thyroid gland x 100-180MiCi/ gm
- 185-555MBq
outcome at 4-8 weeks
increasing the dose increases the change of hypothyroidism which also increases with time

102
Q

what do large doses of iodine 131 do

A

minimise potential morbidity quickly which results in certain hypothyroidism

103
Q

what is the process of radioiodine therapy

A

order capsule 72 hours prior
measure activity within 10% of prescribed dose
stop antithyroid med 3 days prior
remove dentures
dont chew
hot drink after administration or water

104
Q

who is not given RIT

A

pregnant women
<10 years

105
Q

what are the pre-cautions for thyrotoxicosis RIT

A

cardiac arrest
contact RPA or RPS
dont do mouth to mouth
gloves and apron
film badge
shielding for crash team
death enclosed fully in plastic bag

106
Q

when should they avoid public transport

A

> 400 MBq
should avoid crowds as well

107
Q

what advice should be given

A

should sleep away from partner
wear kitchen gloves

108
Q

when should you stay away from work

A

> 400MBq

109
Q

when should you avoid contact with others

A

adults: >150
children: >30

110
Q

when should you remain in hospital

A

> 800MBq

111
Q

what are the issues with RIT

A

vomiting
If disease is not controlled then further doses are given
- 50% patients feel better after 3 months
- 50% need 2/3 treatments to get desired control

subsequent hypothyroidism is treated with thyroxin
risk: leukaemia, thyroid cancer, gene mutations in repro cells

112
Q

post iodine follow up

A

at 6 weeks, 12 weeks [free test T4 + TSH]
6 months, 1 year and then annual life long follow up

113
Q

what are hypothyroid symptoms

A

over weight, sluggish, leathery skin,

114
Q

patients with thyrotoxicosis what percent become hypothyroid after 2 years

A

50

115
Q

what increases the risk of a hypothyroid

A

small goitre size
family history of autoimmune thyroid disease

116
Q

what are the signs of hyperthyroidism

A

twitching
palpations
warm skin
red palms
loose nails
urituria
patchy hair loss
eye problems

117
Q

symptoms of hyperthyroidism

A

hyperactivity
mood swings
difficulty sleeping
tired
frequency
persistent thirst
itchiness
loss of interest in sex

118
Q

what is graves opthalmopathy

A

overproduction of thyroid hormones, enlarging the fat pads pushing the eyes forward increasing pressure on the bony orbit affecting the extra-ocular muscles, can lead to blindness

119
Q

what is the dose prescription for graves opthalmopathy

A

20Gy in 10 [very responsive]

120
Q

what is the technique for graves opthalmopathy

A

POP
angle 5% posterior taking away from the lens
1/2 beam block to only treat the back of the eye
50% isodose to the pituitary gland

121
Q

what is the TV for graves opthalmopathy

A

orbit fat + extraocular muscles
want to treat tissues behind the eye

122
Q

position for RT for graves opthalmopathy

A

supine
shell
CT

123
Q

what are the side effects to RT for graves opthalmopathy

A

pressure increase = inflammation
dry eyes

124
Q

what is thyrotoxicosis

A

clinical state associated with
the raised levels of circulating T3/T4, increased levels of thyroid hormones

Head and Neck and CNS (12 decks)

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